University:
Western Sydney University
Course:
MEDI 2003 | Clinical Sciences 2
Academic year:

2024
Views:

390

Pages:

1
Author:

Mariam A. A.

Chromosome Structure and gene Expression Chromosome Structure • • • • • Genome: the full set of genetic information that an organism has in its DNA. Chromosome: made of DNA that is wrapped and coiled around histones. Chromatin: - DNA + histone. - For the vast majority of the life of the cell, the chromatin is decondensed. The 46 chromosomes of a human cell are organised in 23 pairs and the two members of each pair are homologous of one another. - One comes from the mother, and one comes from the father. Centromere -> divides the chromosomes into two long arms and two short arms. - The long arms are the q arm and the short arm is the q arm. Arm of chromosome divided into 1 to 4 major regions, each demarcated into several bands by staining. Each band, positively or negatively stained, is given a number, which increases as distance from centromere increases. E.g. 1q23 – chromosome (1), long arm (q), 2nd region distal to centromere (2), and 3rd band (3) in that region Then ends of the chromosomes are called telomeres that are made ot multiple tandem repeats of short DNA sequences. Centromeres of sister chromatids are the site of kinetochore formation (structure forming at centromere during mitosis for binding microtubules and allowing mitotic spindle formation) The ends of chromosomal arms are known as telomeres, consisting of multiple tandem repeats of short DNA sequences. In germ cells and other cellular contexts, additional repeats are added to telomeres by a protein-RNA complex telomerase. Density of genes varies across chromosomes, so that there are gene-dense regions or areas almost devoid of functional genes. Exons are termed nucleic acid coding sequences, which are present in mRNA. Introns are the non-coding sequences present in the hnRNA, which are removed by RNA splicing before translation. - • • • • • • • • Sex Chromosomes: - XX -> female -> 1 X from the mother and 1 X from the father. - XY-> male -> 1 X from the mother and 1 Y from the father. Gene expression: - Transcription and translation.